1. Field of the Invention
The invention relates to an antenna orientation sensor. More particularly the invention relates to a magnetic antenna orientation sensor, capable of self-correction for the presence of hard and soft iron effects.
2. Description of Related Art
To optimize electrical performance, directional antennas are oriented to direct the antenna radiation pattern towards a desired direction. Orientation of an antenna is typically performed via adjustments to the antenna mount, with respect to a fixed mounting point, to vary orientation in, for example, three axis: proper heading, roll and pitch (mechanical beam tilt).
Orientation may generally be performed by manual or remote controlled electro-mechanical adjustment with respect to a reference direction. Orientation may be performed upon installations that are fixed, or dynamically on an ongoing basis during antenna operation to satisfy varying directional requirements and or changes to the orientation of the antenna mount, for example where the communication target(s) are mobile and or the antenna is mounted upon a movable land, air or water vehicle. Magnetic direction sensors typically provide a directional output with respect to the planetary magnetic north pole. A problem with magnetic direction sensors is errors introduced by hard and soft iron effects from nearby metal, such as the mounting of the antenna upon, for example, a metal tower or vehicle. The error level introduced will vary with the location and size of the nearby metal at each installation. Further, the error magnitude may change as the selected antenna orientation varies the location and or orientation of the sensor towards and away from the nearby metal.
Sunlight angle sensors have been applied as an alternative to magnetic direction sensing, however these systems operate only when and where the sun is visible to the sensor and may have a significant initial reading lag time. Also, sunlight angle sensors require periodic cleaning to prevent failure of the sensor due to environmental fouling, a significant drawback where the sensor is difficult and or dangerous to access, such as when mounted atop an antenna tower.
Therefore, it is an object of the invention to provide an apparatus that overcomes deficiencies in the prior art.